Conventionally, avionics engineers and certification bodies are improving and providing pilots and flight crews with information necessary to identify in-flight traffic. An approach has been to provide the flight crew with information on the location of other aircraft in the area. One exemplary system which is capable of providing this information, is known as a traffic alert and collision avoidance system (TCAS). TCAS systems are required for all airliners flying in the United States air space today. TCAS devices have been designed to interrogate transponders of other aircrafts, sometimes referred to as intruder aircraft. The TCAS system evaluates the threat of collision with the other aircraft and coordinates an avoidance maneuver for the aircraft. Another type of traffic information system is known as automatic dependent surveillance broadcast (ADS-B). ADS-B systems are capable of providing position, velocity, and status information broadcast from an aircraft at regular intervals using information obtained from global positioning system (GPS) satellites and onboard systems. ADS-B systems may use the Mode S transponders and provide transmissions at regular intervals. Accordingly, ADS-B transponders need not be interrogated.
In an ADS-B system, a Mode S transponder or a squitter may be disposed in a first aircraft that continuously emits a squitter message. The squitter is a radio frequency (RF) signal that is generated by the radio-based transponder. In an ADS-B system since there is no reply to the ADS-B squitter message, it may be desirable to have knowledge of whether the ADS-B squitter is transmitting properly.
Accordingly, there is a need for a system in which an ADS-B squitter message may be checked by the systems of the transmitting aircraft. Further, it may be desirable to have an ADS-B system which not only determines whether the ADS-B squitter is transmitting but also whether the ADS-B message transmitted is correct.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.